HILO » With luck, the tradewinds that started blowing volcanic fumes away from Volcano Village yesterday will continue today, and Big Island people will be able to breath easy.

Mayor Harry Kim declared in a radio message late yesterday that the warning level for sulfur dioxide in the Volcano area was being reduced to Code Yellow, the lowest warning level. At Pahala, now once again in a downwind position, the code also remained yellow.

Since Monday it had been designated as Code Purple, the highest warning level, although few spots actually rose to the purple trigger point of 2 parts per million of sulfur dioxide.

Like a last shot of nastiness yesterday before being blown away, there was bad air in spots all over the island.

In the Volcano Golf Course subdivision, resident Christina Heliker said, "Once or twice it was pretty nasty. It never stuck around more than half an hour or an hour," she said.

Roofers working on her house stayed at their job and worked through it, she said.

At the Volcano Post Office, resident Barry Stokes said, "Every time I inhaled, I had to cough."

At Kulani Prison, 10 miles from the Halemaumau vent, vog got bad enough at times that prisoners doing outdoor work had to be brought indoors as a precaution, said warden Beryl Iramina.

North of Hilo near Honokaa, 45 miles away, retired Dr. Fred Holschuh said the vog was the worst he had ever seen.

In Keauhou, on the other side of the island in Kona, vog was described as "heavy" at noon.

Return of normal or near-normal conditions would allow the reopening of Hawaii Volcanoes National Park. A decision was to be made this morning.

The entire Hawaiian Volcano Observatory staff, instead of a skeleton crew, could return to work analyzing automated data.

The Volcano House hotel and Kilauea Military Camp resort for military families could reopen.

But a new question arose: What hit us?

All of the warnings had been based on measurements of a single gas, sulfur dioxide, just one in a mix of gases and particles emitted by Halemaumau and Puu Oo craters.

Members of the National Guard's 93rd Civil Support Team supplied equipment and personnel for six roving teams gathering data and samples during the two days of high gas levels.

Unit commander Lt. Col. Thomas "Trey" John III emphasized that lab work needed to be done by the state Department of Health and others.

Besides unknowns about what chemicals were in the voggy gas, no one was sure about what big particles in it were and what effect they would have on health, he said.

In the absence of detailed information, officials started to talk less about sulfur dioxide and more about vog, a word that has been around since eruptions started in the Puu Oo area 25 years ago.

County Managing Director Dixie Kaetsu said there was a feeling that vog traveling nine miles from Puu Oo to Volcano might have less harmful sulfur dioxide in it than a plume hitting the village from Halemaumau three miles away.

But the science remained unclear.

The state Department of Agriculture said the effects of volcanic gases on livestock and crops was also unclear. Fluorine, known to harm animals, was found in the volcanic ash, but whether the levels are high enough to be a threat is not known, said Volcano Observatory head Jim Kauahikaua.

At present there are no reports of illness in animals due to the volcanic plume, the Agriculture Department said.